1. Field of the Invention
The present invention relates to sliding windows, and more particularly to sliding windows that are made of a synthetic resin and provided in vehicle roofs.
2. Description of the Related Art
A roof of an automobile may be provided with a sliding window. The window is opened to draw fresh air into the passenger compartment. A typical sliding window 9 is illustrated in FIG. 7. As shown in FIG. 8(a), the window 9 is fit into an opening in the roof 99 of a vehicle. The window 9 may be lowered with respect to the roof 99 and then moved along a pair of guide rails 97 to open the roof 99, as shown in FIG. 8(b).
As shown in FIGS. 7 and 9, the window 9 includes an inorganic glass 91, a molding 92, and a weather strip 93. The molding 92 encompasses the glass 91. The weather strip 93 encompasses the outer side of the molding 92 to seal the space between the window 9 and the roof 99. The molding 92 is made of a relatively hard resin while the weather strip 93 is made of a soft rubber.
As shown in FIG. 9, a washer 951 and a fastener 952 is attached to the bottom surface of the molding 92 near each side of the glass 91. An elbow-like bracket 962 is held by the fastener 952. A shaft 961, which supports a roller 96, is coupled to the bracket 962. The roller 96 rolls along the rail 97. This simple sliding structure enables opening and closing of the window 9.
During recent years, it has become preferable to use a transparent synthetic resin plate for the sliding window instead of the inorganic glass. A resin plate is lighter and has a better appearance than inorganic glass. When employing a resin plate, it is preferable that major changes are not required in the above sliding structure. In other words, it is preferable that a sliding window employing a resin plate have the same highly reliable structure as the prior art sliding window in which the structure enables sealing of the space between the window and the roof and also enables opening and closing of the window.
However, the linear expansion coefficient of a synthetic resin is greater than that of an inorganic glass. When the vehicle travels, the outdoor temperature causes expansion or contraction of the resin plate. The deformation of the glass results in degradation of the sealing ability between the sliding window 9 and the roof 99. This may degrade the comfortable environment in the passenger compartment.